Here's a brief background:
In January, I moved in with my aunt and uncle in Ottawa to take pre-university classes. Well, the first semester I was a bit overwhelmed, lol.
This semester, though, I thought it would be nice if I could have something to keep me company. Back at home I have a cat, but my aunt is allergic, and my uncle is finicky about animals in the house.
He keeps a fish tank though, so I think you can see where this is leading...

He very generously gave me a 10 gallon tank that he wasn't using, and so I decided to divide it between a pair of Bettas.

I haven't had much experience with Bettas, to be honest. I had a pair in a 5 gallon tank, but didn't care for them as well as I should for the lack of knowledge I had when I was younger.
I also kept a female in a very large (possibly 3 gallon) vase. She was a real cutie, white with pinkish/red fins and a black raccoon mask on her face!

So here I am with my 10 gallon tank, and I have a couple of questions about it:

1. I really like more natural looks, so i want to get sand. I don't like gravel very much. I've heard that you can use regular playsand, but I saw some 'Hermit Crab' sand at Petsmart today and was wondering if that was safe to use in a tank? It was a very pretty black colour which caught my eye. If not, I'll just stick to the regular stuff.
I asked the girl there, and she said I shouldn't be using any kind of sand in my tank because it's toxic to the fish.

2. The tank my uncle gave me is rather dirty, with white streaks that I'm assuming to be calcium build-up on it. I don't want to use bleach. A site I looked up suggested vinegar, but wasn't really specific about it. I was just wondering if there's a certain amount you need to add?

Also, is there anyone else here from the Ottawa area? If so, I'd really like it if you could point me out to the fish/petstores you like to go to. I'm from a smaller city and the place is rather daunting, lol.

I just bought some vinegar last night, so I'll clean it tonight. I haven't been able to find an answer about the Hermit Crab sand, so I guess I'll just stick to regular sand.
It did say non-toxic on the label, but do you think it might add something weird to the water? :s

I believe I would stick with regular play sand. I fear the sand (although I don't know) for hermit crabs ,may or may not contain minerals to help with crabs shell development and may raise ph to undesireable levels. This is only a guess on my part but I might check to see if hermit crab sand contained minerals such as calcium. If so,, or content was not listed,, I wouldn't use it.